Scrolling

For other uses, see Scroll.

In computer graphics, movies, television, and other kinetic displays, scrolling is sliding text, images or video across a monitor or display. "Scrolling", as such, does not change the layout of the text or pictures, or but incrementally moves (pans or tilts) the user's view across what is apparently a larger image that is not wholly seen. A common special effect is to scroll credits, while leaving the background stationary. Smooth scrolling is a feature to reduce what the viewer would perceive as "jumps" (discontinuous movement) in the display. The computational effort of moving images and video smoothly is high, therefore successful smooth scrolling in text is most common. Frame rate is speed at which an entire image is redisplayed. It is related to scrolling, in that changes to text and image position can only happen as often as the image can be redisplayed. When frame rate is a limiting factor, one smooth scrolling technique is to blur images during movement that would otherwise appear to "jump".

Scrolling can also refer to a certain misbehavior conducted in a chat room whereby one person causes the screens of many others in a chat to scroll against their will by inserting much noise or special control characters.

Computing

Scrolling is often done on a computer by the CPU or a graphics card. In a WIMP-style graphical user interface, scrolling is done with the help of a scrollbar or using keyboard shortcuts, often the arrow keys. Scrolling is often a key feature in text user interfaces and command line interfaces, though some older computer terminals used a paging mode instead, akin to flipping through a series of pages in a book, usually using the Page Up and Page Down keys or the space bar. Computer mice may also have a scroll wheel, which scrolls text vertically when rolled. (Most common computer mouse have scroll balls or tilt wheels which allow for horizontal scrolling) Software such as Adobe Reader can also be scrolled with the hand tool. In this case, the document is dragged and moved around like a piece of paper.

Other PC mouse scrolling is available, although function varies widely between software applications. Some scroll wheels can be pressed down, functioning like a button. Depending on the software, this allows scrolling in both the horizontal and vertical directions by dragging in the direction desired; when the mouse is moved to the original position, scrolling stops. A few scroll wheels can also be tilted, scrolling horizontally in one direction until released.

If any content is too wide to fit on a display, horizontal scrolling is required to view all of it. In applications like graphics and spreadsheets, the content often has a 2D structure, and horizontal scrolling can be useful and necessary.

One-dimensional content

Plain text is essentially linear, it does not have a 2D structure. For text in most scripts (with line-by-line ordering of characters on horizontal lines, as opposed to vertical writing), horizontal scrolling is much more inconvenient than vertical scrolling, because when reading the text in order, back-and-forth scrolling is needed for every line, as opposed to vertical scrolling, which is needed only after reading a whole window or column of text.

A web browser normally places as many words in a single line as will fit the width of the browser window. Special HTML-code may instruct the browser to divide the window into columns, in which case it places as many words in a single line as will fit the width of the column.

Demos

Scrolling texts, also referred to as scrolltexts or scrollers, were an integral feature of the majority of the demos written for home computers in the 1980s. They were particularly important in crack intros programmed by software crackers, where they were used to convey messages between groups involved in the activity.

Many scrollers were plain horizontal scrollers, but demo coders also paid a lot of attention in finding new and different types of scrolling. The characters could, for example, continuously alter their shape, take unusual flying paths or incorporate color effects such as raster bars. Sometimes it makes the text nearly unreadable.

Movies

One of the most famous scrolling texts in movies is the Star Wars opening crawl. The text appears at the bottom of the screen and slowly moves upwards and into the distance as the audience reads it.

Television

Scrolling is commonly used to display the credits at the end of television shows.

Scrolling is also used in television news when a news ticker is employed, scrolling news stories horizontally across the bottom of the screen.

Video games

In computer and video games, scrolling of a playing field allows the player to control an object in a large contiguous area. Early examples of this method are Sega's 1977 side-scrolling video game, Bomber, as well as Super Bug. Parallax scrolling, which was first featured in Moon Patrol, involves several semi-transparent layers, which scroll on top of each other at varying rates in order to give the illusion of depth.

A previously much used alternative to video game scrolling is the flip-screen method.